Generally, a twisted nematic (TN) LCD display has a viewing angle which is dependent upon orientations of molecules of the liquid crystal material sandwiched between the panels of the display. To provide wider viewing angles, a domain divided twisted nematic (DDTN) display has been proposed in which a single rubbing process may be used to form a panel of the display which when combined with a similar panel provides alternating twists for liquid crystal molecules of adjacent pixel areas.
As illustrated in FIGS. 1 and 2, a conventional LCD includes a thin-film transistor (TFT) substrate 10 opposed by a color filter substrate 20. Each pixel area defined on the substrate is divided into two regions, a first region covered by a first alignment layer 30a, 30b which provides a first pretilt angle for the liquid crystal material and a second region covered by a second alignment layer 32a, 32b which provides a second pretilt angle for the liquid crystal material, the second pretilt angle typically being greater than the first pretilt angle. The first and second alignment layers 30a, 32a of the TFT substrate 10 typically are rubbed in a first direction (indicated by the dotted arrows of FIGS. 1 and 2) to produce fine grooves in the first and second alignment layers 30a, 32a which are disposed along the first direction. The first and second alignment layers 30b, 32b of the color filter substrate 20 typically are rubbed in a second direction (indicated by the solid arrows of FIGS. 1 and 2) perpendicular to the first direction to produce fine grooves in the first and second alignment layers 30b, 32b of the color filter substrate 20 which are disposed along the second direction. To assemble the display, the TFT substrate 20 and the color filter substrate 20 are mounted in opposing relationship and aligned such that a portion of the TFT substrate 10 which is covered by the first alignment layer 30a is opposite a portion of the color filter substrate 20 which is covered by the second alignment layer 32b. Assuming the top of the page represents the top of the display, if the first and second directions are as indicated in FIG. 1, an "up-down" DDTN structure is provided which can produce a wider vertical viewing angle for the display. In contrast, if the first and second directions are as indicated in FIG. 2, a "left-right" DDTN structure is provided which can produce a wider horizontal viewing angle for the display.
The conventional DDTN structures described above can provide improved viewing angles over non-domain divided displays. However, the viewing angle improvement achieved is typically unbalanced, providing an increase viewing angle in only one direction.